The invention relates to machine tool bed straightness compensating means and, more particularly, it is especially appropriate for use as an apparatus for compensating for deviations in the straightness of the ways of a horizontally extending machine tool, such as a lathe. Still more particularly, its best application is on long machine tools for working large items, such as rolls and beams.
In precision lathes, the straightness of the bed which guides the carriage on which the tool is mounted is very important. Any deviation from straightness in the bed is reproduced in the work pieces. On a roll, for example, such a deviation is increased by a factor of two measured on the diameter. It is one thing to provide accuracy and straightness in a lathe having a bed, say, 20 feet long. It is quite another thing to provide accuracy and straightness in a much larger lathe. It is not uncommon for modern lathes to have beds up to 100 feet in length. Often such beds are made of several sections which are machined, hand scraped, and hand fitted together. It is not possible from a practical standpoint to make beds of this type sufficiently straight for precision work, especially on large rolls which may be 60 inches in diameter and up to 400 inches long.